DAMASCUS, Syria -- Prospects for a Middle East peace conference this month became more certain yesterday, as Syria gave its final approval to plans for the talks even while bitterly denouncing Israel for refusing to return occupied lands to its Arab neighbors.

The Syrian attitude, added to the distrust of the other parties to the conference, appeared to diminish hope that the conference would develop into a discussion of substantive issues.

Syrian Foreign Minister Farouk al-Sharaa said he would not even shake hands with his Israeli counterpart, David Levy, at the start of the talks. Mr. Sharaa also plans to boycott follow-up discussions on regional problems until Israel proves at the bargaining table that it is willing to give up territories it captured in the 1967 Mideast war.

"This very hand is guilty. . . . It is a hand which occupies our lands and ignores Palestinian national rights," Mr. Sharaa said.

In Washington, meanwhile, the White House said it was possible that both President Bush and Soviet President Mikhail S. Gorbachev would attend the opening of the peace conference, which is expected to take place Oct. 29 or 30, either in Lausanne, Switzerland, or The Hague, the capital of the Netherlands.

But Mr. Bush refused to confirm the date and site of the conference or his own participation, saying that "we have no set plans."

The details should be known by the weekend, however, when the United States and Soviet Union -- co-sponsors of the conference -- are expected to send out formal invitations to Israel and its immediate neighbors: Syria, Jordan, Lebanon, Egypt and the Palestinians.

Syria's refusal to participate in a subsequent set of talks on regional issues came as a disappointment to Secretary of State James A. Baker III, who concluded two long days of talks here yesterday with Syrian President Hafez el Assad.

Mr. Baker had hoped that the regional talks, which are to begin two weeks after the start of the main peace negotiations, would create a climate of cooperation that would help Israel and its Arab neighbors through the difficult bargaining on the fate of the occupied lands.

Mr. Baker sought to play down the importance of Syria's position.

"We are still on course to hold a peace conference in this month of October," he said before leaving for Jerusalem last night to nail down firm pledges of attendance from two other vitally needed participants: the Israelis, and Palestinians from the occupied West Bank and Gaza Strip.

"We ought not to . . . suggest that somehow a difference of opinion with respect to that [Syria's boycott of the regional talks] would bar the other two stages, because it won't," Mr. Baker insisted at a news conference with Mr. Sharaa.

Nevertheless, Mr. Sharaa's verbal attack on Israel dramatized how difficult it will be to achieve results once peace talks get under way.

The intractable nature of the land-for-peace dispute was driven home again to Mr. Baker in Jerusalem, where about 1,000 opponents of a peace conference protested the U.S. secretary's arrival for a meeting with a group of Palestinians to discuss who would represent them.

The protesters are part of a right-wing group in Israel adamantly opposed to giving up the territories. They want to expand Jewish settlements in the occupied lands to ensure that the territories are never returned to the Arabs.

Israeli Prime Minister Yitzhak Shamir has tentatively agreed to attend the peace conference. But he has withheld formal approval until he receives assurances that Palestinian delegates a conference are not formally linked to the Palestine Liberation Organization, which Israel considers to be a terrorist group.

At the same time, the PLO has insisted on the right to designate the Palestinian delegation and guide it from a distance.

Mr. Baker's mission in Jerusalem will be to work out a list of Palestinian delegates acceptable to both Israel and the PLO.

As Mr. Baker arrived in Jerusalem, PLO Chairman Yasser Arafat summoned PLO leaders to a secret meeting in Tunis, Tunisia, hoping for a mandate to allow the peace conference to convene.

The regional talks have been a major incentive luring Israel to the peace table because Arab countries without land disputes with Israel -- such as Saudi Arabia and Kuwait -- plan to attend. By doing so, they would tacitly confer recognition on Israel, something the Jewish state has sought since its founding 43 years ago.

The Bush administration fears that a collapse of the regional talks might give Israel a last-minute excuse to back out of the peace conference.

Israeli officials, however, said it was highly unlikely that Mr. Shamir would balk, even though he might want to.